Gaseous conduction apparatus



Sept. 20, 1932. C G sMfTH 1,878,338

GASEOUS CONDUCTION APPARATUS Original Filed Dec. 21, 192 5 @417 mm a W W Patented Sept. 20, 1932 UNITED STATES PATENT, OFFICE.

CHARLES G. SMITH, OF MEDIORD, MASSACHUSETTS, ASSIGNOB: TO RAYTHEON INC, 0]? CAMBRIDGE, MASSACHUSETTS, .A. CORPORATION OF MASSACHUSETTS GASEOUS CONDUOTION APPARATUS Application filed December 21, 1925, Serial No. 78,798. fBenewed September 26, 1931.

This invention relates to gaseous discharge devices generally and particularly to glow rectifiers. Heretofore, gaseous glow tubes have required high voltages to start the gaseous discharge and this re uirement has confined such devices, particu arly gaseous rectifiers, to a narrow field of usefulness The principal objects of the present invention are to enable such devices to start on lower voltages and at the same time make them rugged and durable.

According to this invention the enclosure containing the electrodes contains two asses (or vapors). One gas, herein referre to as the first gas, is an easily ionizable gas, preferably vapor of caesium or other alkali metal or alkali earth metal such as calcium, strontlum or barium. The other gas, herein referred to as the second gas is less easily ionized and preferably has one or more of the followmg characteristics: negligible or low electron a-flinity; passes electronic discharge readily; and inert with respect to the alkali gas. While various gases have certain of the'requisite characteristics, the monatomic gases appear to have all these characteristics, and helium is particularly suitable. By virtue of its low ionization voltage the first gas may be readily ionized by light-radiating means or other auxiliary ionizing means to enable the discharge between electrodes to start on low voltage,'after which the second gas is ionized sufiiciently to maintain the discharge either independently or in'conjunction with the ionization of the first gas. 7

The auxiliar ionizing means is preferably in the form of an incandescent solid. The incandescent solid is particularly efiective when placed inside a hollow cathode.

For the purpose of illustration a rectifier embodying the invention is shown in the accompanying drawing in which E is the enclosure, preferably of glass, C the hollow cathode, A the anode, X a metal shield, F an incandescent filament, P the primary of a the gas in the spaces.

transformer, S a secondary connected in series with the cathode-anode and load, and H a secondary connected to the filament F. The parts A, C, E and X are preferably cylindrical in cross-section. The cathode, anode and shield may be formed pf tungsten or other suitable material. As illustrated the filament is preferably not connected to the load circuit of the rectifier so that its thermionic emission takes no part in the general flow of current, its purpose being merely to emit light and heat. The anode is mounted on a stem at the upper end of the tube and the shield X is mounted upon a stem-at the lower end of the tube. As shown in the figure the cathode is supported by the shield. The spacing between the anode and shield and also between the tube E and the outer peripheries of the anode and shield is preferably so small that electrons traveling directly across either space do not substantially ionize While the two gases above referred to may be incorporated in the tube in various ways, when using caesium and helium the following procedure is recommended: First evacuate the enclosure E; then thoroughly free the electrodes from gas by heating dur-' ing pumping; then distill a small quantit of pure caesium into the enclosure; and fina ly admit helium to the desired pressure, for example 1 cm. For illustration the caesium is indicated at I.

In dperation thefilament F is raised to the proper temperature to produce the desired degree of ionization. If the filament be heated to approximately 2200 C. for example, many of the caesium atoms will be excited by the heat to the radiation voltage level (1.45 volts) so that a large number of caesium molecules are at all times in an excited state. With the molecules (or atoms) in this excited state the relatively small amount of short-wave radiation coming from the filament readily i onizes the caesium suflicathode for ionizing charge to start at low voltage. After the start of the discharge, the filament current may be reduced, or even discontinued,-but it is preferably continued to aid in production of ions near the cathode.

The discharge takes place between the anode and the interior of the cathode throng? the openings in the cathode and shield By making these openings small and passing a substantial discharge the ionized caesium vapor is pumped into the hollow cathode, as described in my application Serial No. 55,262, thereby maintaining a higher pressure of caesium vapor inside than outside the cathode. To maintain this pressure difierential the lead opening through the bottom of the cathode is preferably closed with an insulation plug B.

I claim: g 1. A gaseous discharge device comprising an enclosure containing electrodes including a hollow cathode having a restricted discharge opening, an easily ionizable gas, a second gas having low electron afiinity, and means inside the hollow cathode for ionizing the first gas, whereby an electronic discharge may be started through said second gas on lower voltage.

' 2. A gaseous discharge device comprising an enclosure containing electrodes including a hollow cathode having a restricted discharge openin an alkali vapor, a gas and heat and lig t radiating means inside the hollow cathode for ionizing said vapor, whereby an electronic discharge may be started through said gas on lower voltage.

3. A gaseous discharge device comprising an enclosure containin electrodes including a hollow cathode having a restricted dis-' charge opening, an easily ionizable gas, a second gas having low electron afiinity, and energy radiating means inside the hollow the first gas, whereby an electronic disc arge may be started throu h said second gas on lower voltage.

4. gaseous discharge tube containing a chamber-like cathode having a restricted discharge opening, an anode in spaced relation thereto and a hollow member partially enclosing the cathode, said hollow member being wlthin an insulatingly short distance from the anode and walls of the tube.

- 5. A gaseous conduction device comprising an envelope containing a vapor having a low ionization potential and a gas having a higher ionization potential, a hollow equi- Eotential cathode, a hollow metallic memer surrounding said cathode, said cathode and member having coaxial apertures and an anode s aced an insulatingly short distance from said last mentioned hollow member.

6. A aseous discharge device comprising the com ination with an envelope, of a vapor within the envelope having a low ionization potential and agas having a higher ionization potential, a hollow cathode, a hollow anode spaced from said cathode, a filament within the cathode, a hollow metallic 1118111? ber surroundin the cathode, the said cathode and metallic ho low member being apertured to permit passage ofthe discharge between the electrodes.

7 A unidirectional gaseous discharge device comprising a hermetically sealed vessel containing a cathode having a relatively large efi'ective electrode area, an anode having a relatively small efi'ective electrode area, a gaseous atmosphere in said vessel at a pressure at which. after starting a unidirectional glow discharge will be maintained between said cathode and anode at a redetermined voltage drop but requiring a higher voltage for starting, and a heater in said vessel adj acent said cathode arran ed to be operated at incandescence to lower the starting voltage of said device said anode being arranged relatively to said cathode to eliminate long ionizing paths'along which the reverse voltage on the anode could ionize said gas and produce a. reverse current.

8. A unidirectional gaseous discharge device comprising a hermeticall sealed vessel containing a hollow cathode aving a relatively large interior electrode area, an anode having a relatively small efifective electrode area,-a gaseous atmosphere in said vessel at a pressure at which after'starting a unidirectional glow discharge will be maintained between said cathode and anode at a predetermined voltage drop but requiring a higher voltage for starting, and a heater in said hollow cathode arranged to be operated at incandescence for lowering the starting voltage of said device, said anode being arranged relatively to said cathode to eliminate long lonizing paths along which the reverse volt- .age on the anode could ionize said gas and produce a reverse current.

9. A unidirectional gaseous discharge device comprising a hermetically sealed vessel containing a cathode having a relatively large efiective electrode area, an anode having a relatively small effective electrode area, a gaseous atmosphere including an easy-toionize gas and a difiicult-to-ionize gas in said vessel at a pressure at which after starting a unidirectional glow discharge will be maintained between said cathode and anode at a predetermined voltage drop but requiring a higher voltage for starting, and a heater in said vessel adjacent said cathode surface arranged to be operated at incandescence to initially ionize said easy-to-ionize gas and lower the starting voltage of said device.

10. A unidirectional gaseous discharge device comprising a hermetically sealed vessel containing a hollow cathode having a relatively large interior electrode area, an anode having a relatively small effective electrode area, a gaseous atmosphere including an alkali vapor and a gas in said Vessel at a ressure at which after starting a unidirectlonal glow discharge will be maintained between said cathode and anode at a predetermined voltage drop but requiring a higher voltage for starting, and a heater in said hollow cathode arranged to be operated at incan descence to initially ionize said vapor and lower the starting voltage of said device, said anode being disposed close to said cathode and arranged 1n the vessel to eliminate long ionizing paths along which the reverse voltage on the anode could ionize said gas and produce a reverse current.

11. A unidirectional gaseous discharge device comprising a hermetically sealed vessel.

containing an anode, a cathode structure having an extended electrode surface and const1- said cathode electrode tuting an enclosure around the space in front of said electrode surface, said enclosure having a discharge opening, an ionizable gas in said vessel in a quantity sufiicient to sustain a space discharge between said anode and said cathode electrode surface at a voltage of the order of the cathode glow fall or less an electrical heater within said enclosure for heating and exciting the gas therein and producing a discharge between said cathode electrode surface and said anode, and an independent electric energizing circuit for said heater, said energizing circuit being insulated from the circuit of the discharge in said device.

12. A unidirectional gaseous discharge device comprising a hermetically sealed vessel containing an anode, a hollow cathode constituting an enclosure around a part of the space in said vessel and having an extended interior solid electrode surface, said enclosure having a discharge opening, an ionizable gas in said vessel in a quantity sufficient to sustain a space discharge between said anode and said cathode electrode surf-ace at a voltage of the order of the cathode glowjall or less, an electrical heater exposed within said'enclosure for heatin and exciting the gas therein and producing a discharge between surface and said anode, electric energizing cirsaid energizing c1rcuit thecircmt of the disand an independent cuit for said heater, being insulated from charge in said device.

13. A unidirectional gaseous dischargedevice com rising a (gas tight envelope containing a hol ow catho e having a large-area interior electrode area, an anode arran ed to maintain a unidirectional discharge with the interior of said cathode,a gaseous filling at a pressure sufiicient to maintain a unidirectional glow discharge between said anode and the interior of said cathode, means associated Signed by me at Boston, Massachusetts, this tenth day of December, 1925.

CHARLES G. SMITH. 

